Seed Layer Crystal Phase Tuning for Low-Temperature FeRAM
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Solution Overview
Problem
Existing methods for forming ferroelectric materials in FeRAM devices require high annealing temperatures, which can damage metal lines and vias, leading to degraded polarization performance and device integrity.
Innovation Solution
The use of a seed layer with a well-controlled tetragonal or orthorhombic crystal phase to facilitate the formation of ferroelectric layers at lower temperatures, protecting metal lines and vias while maintaining polarization performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If high annealing temperatures are used to form ferroelectric materials, then ferroelectric layer formation is achieved, but metal lines and vias are damaged
Solution Approach 1:
A seed layer is introduced as an intermediary between the metal electrode and the ferroelectric layer. This seed layer has a specific crystal structure that facilitates low-temperature formation of the ferroelectric layer while protecting the underlying metal lines and vias from high temperature damage.
Solution Approach 2:
The seed layer is formed in advance before depositing the ferroelectric layer. This preliminary crystal structure preparation enables the ferroelectric material to form at lower temperatures, preventing thermal damage to metal interconnects while ensuring proper ferroelectric phase formation.
2Reliability
If high annealing temperatures are used, then ferroelectric material forms, but polarization performance degrades
Solution Approach 1:
The invention changes the temperature parameter from high to low by introducing the seed layer. The seed layer's specific crystal structure allows the ferroelectric material to achieve proper polarization at lower annealing temperatures, thereby maintaining high polarization performance while avoiding thermal degradation.
Solution Approach 2:
The seed layer provides a specific crystal phase that facilitates the phase transition of the ferroelectric material at lower temperatures. This controlled phase transition ensures proper ferroelectric properties and polarization without requiring high temperatures that would degrade performance.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for the formation of ferroelectric layers with improved performance and integrity of metal lines and vias, enabling efficient and reliable operation of FeRAM devices.
Implementation Method 1
a first seed layer is deposited over the bottom electrode; performing a surface treatment on the first seed layer, wherein after the surface treatment the first seed layer includes at least one of a tetragonal crystal phase and an orthorhombic crystal phase
Implementation Method 2
performing a thermal operation on the dielectric layer to thereby convert the dielectric layer into a ferroelectric layer
Data Source
AI summary
A method includes: providing a bottom layer; forming a first transistor over a substrate; forming a bottom electrode over the transistor; depositing a first seed layer over the bottom electrode; performing a surface treatment on the first seed layer, wherein after the surface treatment the first seed layer includes at least one of a tetragonal crystal phase and an orthorhombic crystal phase; depositing a dielectric layer over the bottom layer adjacent to the first seed layer, the dielectric layer including an amorphous crystal phase; depositing an upper layer over the dielectric layer; performing a thermal operation on the dielectric layer to thereby convert the dielectric layer into a ferroelectric layer.